1. Field of the Invention
This invention relates to an apparatus for feeding a large external roll of web material into a printer and aligning it therewith. More particularly, this invention relates to a web infeed device that provides proper tension on the web as it is received from an external roll and fed into a printer or other similar web-handling device.
2. Background Information
Some web-handling devices require that the web be properly aligned and under sufficient tension as it passes through the device. For example, certain single-pass duplex printers require a steady web tension, as the web passes through the printer, to maintain registration of a multiplicity of print drums. An example of these types of printers is the full process color printer family developed and manufactured under the trademark Xeikon, such as the printer shown and described in U.S. Pat. No. 4,499,093, which is expressly incorporated herein by reference. The present invention is specifically adapted for this line of printers, however, it is capable of accommodating other web-handling devices that require accurate alignment and tensioned web.
Single-pass multiple station printers, such as the printer shown and described in U.S. Pat. No. 4 499,093, include a plurality of toner image-printing electrostatographic stations. Each station has a drum onto the surface of which a toner image can be formed. An exposure station forms an electrostatic toner image line-wise on each drum surface. A corona device transfers the toner image onto the web, which is conveyed in succession past the stations in synchronism with the rotation of the drum surface. A register control device is provided for controlling the operation of each of the stations in timed relationship thereby to obtain correct registering of the distinct toner images on the web. The register control device includes an encoder driven by the displacement of the web to produce pulses indicative of web displacement, and delay system arranged to initiate the operation of subsequent stations after a predetermined web displacement, as measured by the encoder, has occurred. These types of printers enable accurate registration of transferred images, irrespective of the speed of the paper web through the printer, provided proper tension is maintained in the web throughout the printer.
These printers were designed to accommodate small internal rolls of web material (up to 18xe2x80x3 diameter), using an internal roll stand. To achieve proper tension in the web material, when using an internal roll of web material, a weighted friction pad drags on the surface of the roll as web is fed into the printer. In order to accommodate larger diameter rolls of web material, external roll support and feed apparatuses, such as those described in U.S. Pat. No. 4,893,763 and in several continuation patents and applications, owned by Applicant, which patent is expressly incorporated herein by reference, are required. The rolls fed by this patent are several hundred pounds in weight and have a diameter of three to four feet when full.
One of the significant drawbacks with the use of external roll feeding machines is that it can be difficult to align the web material with the printer intake port. To achieve proper alignment between the external roll apparatus and the printer, an infeed module is used. These infeed modules are placed between the external roll apparatus and the printer and operate to align and tension the web as it comes off the roll and is fed into the printer. Current infeed models work for a limited range of web materials, as long as operators are careful to align the web path between the roll unwind device and the infeed module of the printer.
Prior infeed devices designed for this particular set of printers are portable, yet limited to a relatively narrow range of web materials that they can accommodate, typically 130 to 180 grams per square meter (gsm) papers, while the printer itself can handle papers from 60 to 250 gsm. One such device incorporates a curved-metal shoe and a spring-loaded brush to provide some drag tension on the web. Another limitation with this device, although they employ xe2x80x9cearsxe2x80x9d as web edge guides, they still require very accurate alignment of the web with the printer infeed section (the xe2x80x9cPRSxe2x80x9d). These devices typically are unable to provide sufficient and controllable tension and are difficult to thread up.
Accordingly, it is an object of the present invention to provide an improved portable infeed module, one that in particular has a very wide tolerance for web misalignment coming into the infeed, is simple in design and supports a fill range of paper weights (at least 60 to 350 gsm). This module should enable feeding of continuous web from a large, externally mounted roll on a driven roll stand. It is another object of the present invention that the improved infeed module is easy to thread up and that it does not require any modification to the existing printer paper supply.
To accomplish the foregoing and other objects, features and advantages of the invention there is provided an apparatus for feeding a large external roll of web material into a printer and aligning it therewith. In addition, the disclosed apparatus provides needed tension on the web as the web is drawn into and through the printer.
The apparatus of the present invention comprises a portable infeed device that may be attached to a printer. Preferably, the infeed device is secured to the printer along its housing or other dedicated structure. On certain makes and models of the printer device, the infeed device may be clamped to a pair rails normally dedicated to hold a small internal paper roll. As web is unwound from the external roll apparatus, it forms a free loop between the external roll apparatus and the infeed device. The web enters the infeed device from the free loop into a narrow gap formed by a pair of parallel rods with adjustable edge guides that define the edges of the web path.
After the web passes the parallel rods it passes between a smooth metal shoe and a spring-loaded pressure pad. The spring-loaded pressure pad presses the web against the smooth metal shoe, which operates to create the primary drag force on the web. After passing the tensioning mechanism, the web, now under tension, is pulled around a curved smooth metal surface, extending from the shoe area, which imparts an additional amount of tension on the web. The curved smooth metal surface helps to maintain proper tension on the web as it passes through the rest of the printer.